It is desirable to automatically adjust the vertical orientation of the air flow from an air supply register, accordingly with the temperature of the supply air. Indeed, when the air flow is cool, it should be directed toward the ceiling of a room to prevent cold air from falling directly onto persons nearby. On the other hand, when the air flow is warm for winter heating, it should be directed toward the floor to prevent air stratification.
U.S. Pat. No. 3,298,298 issued in 1967 to Iwata, discloses a system for accomplishing the same function. The register slats 18 are controlled by a bellows 6, for automatically adjusting the direction of a flow of air through the register, upon change in the temperature of said flow of air. The register slats 18 are pivoted at their intermediate section to a peripheral frame through horizontal axes 19. Bellows 6 has gas sealed therein and is located within an air supply duct from an air conditioning unit. A horizontal arm 23 extends laterally of the bellows and carries a vertical common link 21 pivoted to the slats at 29, for rotating all the slats 18 about their pivotal axes upon reciprocating motion of the bellows during temperature changes.
The assembly of the bellows 6 and its return spring 15 occupies substantial space since the bellows must have a large volume for the gas to exert sufficient slat pivoting force under temperature variations. This causes an obstacle to the flow of supply air.
When the register is already installed and has slats which must be manually adjusted and therefore must have sufficient resistance to rotation to keep their adjusted position, then an automatic slat pivoting system using gas filled bellows would be impractical because of the large bellows volume which would be required.
Moreover, since the thermal fill in the bellows is a gaseous compound, the bellows stroke is not a linear function of the temperature variation. This is undesirable, in that control of the orientation of the slats within the desired temperature range is not progressive.
And what is more, the hinge mounts 29 for hingedly mounting each slat 18 to the vertical link 21, require a slot in each slat, rendering the actuator mechanism unsuitable for existing, already installed louvers.